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The whole string now displays like this: 'f�r'.Ī poorly implemented text editor might save the replacement in UTF-8 form the text file data will then look like this: 0圆6 0圎F 0xBF 0xBD 0x72, which will be displayed in ISO-8859-1 as 'fï¿½r' (this is called mojibake).

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Therefore, a text editor could replace this byte with the replacement character symbol to produce a valid string of Unicode code points. The first and last byte are valid UTF-8 encodings of ASCII, but the middle byte ( 0xFC) is not a valid byte in UTF-8. This file is now opened with a text editor that assumes the input is UTF-8. It is usually seen when the data is invalid and does not match any character:Ĭonsider a text file containing the German word für (meaning 'for') in the ISO-8859-1 encoding ( 0圆6 0xFC 0x72). It is used to indicate problems when a system is unable to render a stream of data to a correct symbol. The replacement character � (often displayed as a black rhombus with a white question mark) is a symbol found in the Unicode standard at code point U+FFFD in the Specials table. Its block name in Unicode 1.0 was Special. Unicode's U+FEFF BYTE ORDER MARK character can be inserted at the beginning of a Unicode text to signal its endianness: a program reading such a text and encountering 0xFFFE would then know that it should switch the byte order for all the following characters. They can be used to guess a text's encoding scheme, since any text containing these is by definition not a correctly encoded Unicode text.

U+FFFD � REPLACEMENT CHARACTER used to replace an unknown, unrecognized, or unrepresentable characterįFFE and FFFF are not unassigned in the usual sense, but guaranteed not to be Unicode characters at all.

U+FFFC OBJECT REPLACEMENT CHARACTER, placeholder in the text for another unspecified object, for example in a compound document.

U+FFFB INTERLINEAR ANNOTATION TERMINATOR, marks end of annotation block.

U+FFFA INTERLINEAR ANNOTATION SEPARATOR, marks start of annotating character(s).

U+FFF9 INTERLINEAR ANNOTATION ANCHOR, marks start of annotated text.

Of these 16 code points, five have been assigned since Unicode 3.0:

Specials is a short Unicode block of characters allocated at the very end of the Basic Multilingual Plane, at U+FFF0–FFFF.

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